Bash Scripting Cheat Sheet

VAR="hello"

echo "${VAR}"

${VAR:-default}

${#VAR}

${VAR^^}

${VAR,,}

${VAR/old/new}

${VAR//old/new}

$(command)

readonly PI=3.14

if [[ -f file ]]; then ...; fi

if [[ -d dir ]]; then ...; fi

if [[ -z "$VAR" ]]; then ...; fi

if [[ -n "$VAR" ]]; then ...; fi

if [[ "$A" == "$B" ]]; then ...; fi

if [[ $NUM -gt 10 ]]; then ...; fi

if command; then ...; fi

[[ -f f ]] && echo "exists" || echo "no"

for f in *.txt; do echo "$f"; done

for i in {1..10}; do echo $i; done

while read -r line; do echo "$line"; done < file

while true; do ...; sleep 5; done

for arg in "$@"; do echo "$arg"; done

my_func() { echo "Hello $1"; }

local result="value"

return 0

result=$(my_func "arg")

set -e

set -u

set -o pipefail

set -euo pipefail

trap 'cleanup' EXIT

command || { echo "failed"; exit 1; }

arr=(one two three)

${arr[0]}

${arr[@]}

${#arr[@]}

read -p "Enter name: " name

command > out.log 2>&1

command 2>/dev/null